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Major B. Bhikshapathy, Dr. V.M. Pandharipande, Dr. P.G. Krishna Mohan / InternationalJournal of Engineering Research and Applications (IJERA) ISSN: 2248-9622

www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.865-873

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Analysis & Design of Portable Video Transceiver

Major B. Bhikshapathy *, Dr. V.M. Pandharipande **, Dr. P.G. KrishnaMohan***

*(Professor ECE, Aurora’s Scientific & Technological Institute, Hyderabad) **(Vice Chancellor, Dr Ambedkar University, Aurangabad,)

***(Professor (Retd), JNTU College of Engineering,Hyderabad)

AbstractAll of us enjoy live transmission of

games, adventures and festivals etc. Generally,live recording of program is sent is sent bymeans coaxial cable from place of activity toVSAT equipment some where out side oractivity recorded in CD is physically sent. Thenit is transmitted via satellite. Portabletransceiver with suitable communication rangewill be very handy to transmit video from placeof activity to VSAT. Similarly, there are numberof vital applications of portable (man-held)video transceiver like monitoring the enemyactivities at borders or live reporting on earthquakes, Tsunami etc. Man-held transmitters cannot transmit high powers to avoid healthhazards of the operator. With increased power,equipment becomes bulky also. There is need tooptimize various parameters of transceiver sothat RF Power requirement is minimized. Thispaper analyses all important parameters of Video transceiver, develops suitable formulae/ values for them. It optimizes the parametersusing a simulation model and brings out variousoptions of designing the Video Transceiver asper the user requirements.

Key Words: Band width of transmission, Bit Rate,Foliage Loss, Portable Transmitter, Rain

Attenuation, System Noise Temperature .

1. IntroductionTransmission of live Audio-Visual (A/V)

programs like games, VIP functions and festivals isgenerally carried out by video filming by thePhotographer. The camera output is coupled by acable to the VSAT equipment placed some whereout side the place of activity. At times it becomes

difficult to have a cable connection and recordedvideo program in cassette/CD is physically sent tothe VSAT. It will be very convenient for the newsgathering team, if they have a mobile transceiverfor wireless communication up to VSAT. There areother vital applications of mobile (man-held) A/Vtransceiver, like monitoring the enemy area at theborders or coverage of earth quake, floods,Tsunami etc, where road connectivity may not beavailable at times and communication rangerequired may be more.

Video transmission requires larger bandwidthcompared to voice transmission. If the video istransmitted without compression it requirestransmission rate of at least 10 Mbps [1-3]. Byusing image compression and suitable type of digital modulation the bandwidth can be reducedconsiderably. If receiver’s band width is more,received noise power will be more. To producedesired C/N ratio, the received signal power levelhas to be increased. In case of man-heldtransmitter, the RF power can not be increasedbeyond certain level to avoid health hazards of operating personnel [4]. Besides transmittedpower, received signal power depends on path lossdue the distance between transmitter and receiverand rain attenuation etc. Design requiresoptimization of transceiver parameters to fulfil theuser requirements such as quality of videoinformation, communication range required etc.This paper analyses all important parameters,develops formulae and values for them forsimulation. It brings out a simulation model usingwhich the designer can optimize the parameterssuitably and develop a Video Transeciveraccording to the user requirements.

2. Block Diagram

Fig.1 Block diagram of simulation model of mobile video transceiver

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Legend: All Values are in dBs

Pt - Power Transmitted ;

Gt- Gain of Transmitting Antenna

LDtr- Path Loss due to Distance between Transmitter and Receiver

RA- Rain Attenuation due the rain in the transmission path

Lfr- Additional loss due to use of higher frequencies

Gr- Gain of Receiving Antenna

Lf- Foliage Loss due to trees

Ghra- Gain due to Height of Receiving Antenna

Pr- Received Power by the Receiver

K- Boltzmann’s Constant

Tsky- Noise Temperature at the input of the receiver due to sky noise

Trf- Noise Temperature of the receiver RF Amplifier

Bn- Bandwidth of Noise (receiver)

Pn- Noise Power at the receiver

C/N- Carrier to Noise Ratio (at the input of the demodulator) of the receiver

The parameters shown in the block diagram are explained in succeeding paragraphs. C/N ratio is calculatedusing this diagram.

2.1 Path Loss due to distance between transmitter and receiver (LDtr) There are number models to work out the path loss. To analyse and compare these models path loss has beencalculated for a typical transceiver whose specifications are given below:-

(a) Transmitter Power Output : 5W(b) Transmitter Antenna Height : 2m (Height of man)(c) Transmitting Antenna : Omni Directional Rod Antenna(d) Receiving Antenna : Directional, 1m dia parabolic with 60% efficiency

(e)

Frequency of Operation : 2 GHz(f) T-R Separation : 15 Km max

Summary of the path loss calculated is shown at Table No.1.

TABLE.1 Summary of path loss for suburban areas

S No Model Path Loss (dBm)1 Free Space Propagation Model 142

2 Log-distance Model 1883 Okumura Model 152.214 Hata Model 215.295 PCS Extension to Hata Model 222.526 Lee Model 164.7

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As shown in the Table.1, there is a large variation in path loss calculated using existing models.

To ascertain path loss applicable, field trialshave been conducted [5].

2.1.1 Path loss measured in field

Since there is no transmitter available forconducting this experiment, study has been carriedout using the existing Cellular Mobile Base StationTransmitters for voice/data communication.

2.1.2 Experimental setup The signal strength was measured at various placesusing the following method:-

a) A Laptop having the net monitoringsoftware is used to monitor the signalstrength. It gives, Cell Id, the signalstrength in dBm.

b) A GPS is used to find out latitude andlongitude (Latlong) of any place, toweretc. It also gives the distance between anytwo places whose Latlong is known.

2.1.4 Field conditions a) Location: The Area of observations is in

the outskirts of Secunderabad along

Hyderabad- Karimnagar High way andKushaiguda- Keesara road. Both are Sub-urban Areas.

b) Atmospheric Conditions: Dry, NormalTemperature of about 32 degree Celsius,Clear

c) Sky, Winter Season, between 10 AM and4 PM.

d) Ground Conditions: Approximately plain,with no hills etc.

e) Foliage: There is no dense forest. Onlyfew trees here and there.

f) Rain : No rain was there during theobservation period.

2.1.3 Service conditionsa) Frequency of Operation : 900 MHzb) Service Provider : Airtelc) Type of Service : Voice , 2Gd) Band width of Channel : 4 KHze) Tower Height :10m Appx

2.1.5 Experimental results : Data obtained is tabulated in Table 2

TABLE 2. Data of signal strength measured in field (suburban area)

SNo

CellId

BSIC(BCCH)

RSSIdle

(dBm)Latitude Longitude

DistanceBetween

SerialNos

Appox.Distance

FromCell

site(Km)

PathLossSlope

(dB/dec)

1 6001 01(56) -54 17.55971 78.54453 - 0.5 -2 6001 01(56) -75 17.56688 78.55403 1-2 1.79 37.93 6001 01(56) -86 17.57373 78.56593 2-3 3.27 424 6001 01(56) -97 17.59774 78.56861 3-4 6.69 35.45 50821 52(41) -82 17.57373 78.56596 - 3.0 -6 50821 52(41) -87 17.58003 78.57456 5-6 4.15 35

7 50822 21(37) -75 17.57373 78.56593 - 1.5 -8 50822 21(37) -84 17.58003 78.57456 7-8 2.65 369 843 56(38) -61 17.59774 78.56861 - 1.0 -

10 843 56(38) -78 17.61108 78.57073 9-10 2.5 42.711 53212 10(35) -74 17.62159 78.57121 - 1.5 -12 53212 10(35) -84 17.61239 78.57198 11-12 2.53 4413 37121 15(39) -78 17.50498 78.62689 - 1.5 -14 37121 15(39) -90 17.51267 78.64190 13-14 3.33 34.6

Legend: BSIC – Base Station Identity Code BCCH – Broadcast Channel

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2.1.6 Path loss slope calculations The formula used for path loss slope calculation is as under:-Path Loss (in dB) = (Path Loss Slope) ( log 10 (T-R separation )).For Ex, Path Loss Slope 40 dB/dec means pathloss will be 40 dB if T-R Separation is increased by 10 times.

2.1.7 Conclusions on path loss slopea. From Table No 3.1 above, the path loss slope is varying from 34.6 to 44. By averaging, the

path loss slope is about 38.45 dB /dec.b. This Path loss slope is tallying with 40 dB/dec of Lee Model.

As per Lee Model, Power received in mobile environment is given by [6]

1 1 2156 40 log 20 log 10 logr t t mP P r h h G G (2.1)

Where Pt is transmitted power in dBm;

r1 is T-R separation distance in miles

h1 is height of transmitting antenna in feet;

h2 is height of receiving antenna in feet

G t is gain of transmitting antenna in dBs; G r is the gain of receiving antenna in dBs

Therefore, the path loss, 40log 1 Dtr L r dB (2.2)

2.2 High frequency loss (Lfr)The expression 2.1 is applicable for frequency of 900 MHz [6]. To cater for higher frquencies, an additionalloss factor (Lfr) has been incorporated in simulation model as

Lfr (db) = 10 log 10 (f/0.9) 2, where f is in GHz.

2.3 Foliage loss (Lf)Foliage Loss is the loss in received signal strength due to presence of trees (forest) in the transmission pathbetween transmitter and receiver. There are number of models to calculate the Foliage Loss [7] based on Depthof Foliage in metres (Df). Summary of Foliage Loss is given at Table 3.

TABLE 3. Summary of foliage loss in dBs (for f=2 GHz)

S.No. Depth (d)In meters

WeissbergerModel

Early ITUModel

LeeModel

1 100 24 31 19

2 200 36 47 25

3 300 46 60 29

4 400 54 71 31

5 500 * 81 33

6 1000 * 123 39

*Model not applicable

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Analysis:- Weissberger model is applicable for dense trees only. Early ITU model is impractical at higherfrequencies[7]. Compared to these two models, Lee model is more practical for general forests (which are notvery dense). As per Lee Model [6],

(a). L f increases with frequency as (f)4

(b). L f is 3dB for depth 800m, Foliage away from Tx & 5dB for depth 320 m, Foliage nearer to Tx

(c). L f is 20 dB/dec at 800 MHz

The formula for Foliage Loss designed to be used for simulation is4

10log 3 20log800 100

F

f d L

(2.3)

Where f is the frequency in MHz and d is the depthof foliage in meters.

I term is included to cater for high frequencies ,II term to cater for 3 dB loss at 100m as referenceand the III term indicating 20 dB/dec loss isapplicable for 800 MHz.

2.4 Rain attenuation (RA) in dBs

Presence of rain in the transmission path causesattenuation in received signal power called RainAttenuation. To cater for this rain attenuation,generally a Link Margin of 6 dB is provided inaddition to the minimum C/N required for thereceiver demodulator for satellite link. With 6 dBLink Margin one can assure 99.5% reliability,equivalent to communication loss of 44 hours ayear [8].

In addition, rain increases the antenna noisetemperature. This increase in antenna noisetemperature,

bT is given by [8]

4.34280 1 A

bT e K where A is the rain

attenuation in dBs.

Analysis:- Since Slant Path of rain is more in

mobile communication, due to less elevation angle,the link margin to cater for heavy rain may beincreased to 10 dB. However for moderate rain 6dB may be sufficient. For 6 and 10 dB rainattenuation the increase in antenna noisetemperature works out for 23 and 24 dbrespectively. So the variables for simulation aretaken as: For Heavy Rain – 34 dB, Moderate Rain-29 dB and No Rain – 0 dB.

2.5 Noise power in the receiver (Pn)

Noise Power in the receiver (Pn) is given by[4] Pn= K + Ts + Bn

Where K is Boltzmann’s constant, -228.6dBW/K/Hz; Bn is the Band width of transmission

and Ts is the System Noise Temperature.

2.5.1 System noise temperature (Ts)It is given by [4], s ANT RF T T T

Where ANT T

is the Antenna Noise Temperature and RF T is

Noise Temperature of RF Amplifier of the receiver.The antenna noise temperature depends on antennacoupling to all noise sources in its environment aswell as on noise generated within the antenna.Antenna elevation affects the antenna noisetemperature. Antenna noise temperature decreaseswith increase of elevation [8]. The antenna noise

can be divided into two types of noise according toits physical source: noise due to the loss resistanceof the antenna itself and noise, which the antennapicks up from the surrounding environment.Antenna Noise Temperature varies between10 Kand 100K depending on the frequency andelevation angle. At 2 GHz, it is 100K max.Atmospheric noises just above the surface of theearth will be affecting the antenna noisetemperature. The noise temperature atapproximately zero elevation angle (horizon) isabout 100 to 150 K [8] .

Analysis :- For simulation, we may consider thatmaximum antenna noise temperature to be about150K. Secondly, Noise Temperature of RFamplifier is depending on the quality of thereceiver. For good quality receiver T RF varies from60K to 120K . So the maximum value Ts, 270K (24dB) is used for simulation.

2.6 Band width of transmission Band width of transmission depends on the Type of Signal, Quality of Signal required, Resolution andType of Modulation scheme.

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2.6.1 Type & quality of Signal : The data rate of digital video signal varies depending on theresolution and compression ratio. For the sake of

analysis, the Type of Signal can be represented bythe programs Sports, News or Film. Type &Quality of Signal along with resolution decide theBit Rate (Rb) [10] as shown in Table 4.

TABLE 4. Relation of signal, quality and bit rate

S.No.

Signal Quality Resolution Bit Rate (Rb)

a) Sports Good 704 X 576 6 Mbps

b) Sports Average 544 X 576 4 Mbps

c) News Good 544 X 576 3 Mbps

d) Film Good 544 X 576 2 Mbps

e) Film Average 352 X 576 0.7 Mbps

2.6. 2 Type of modulation & Band widthBand width required varies with type of modulation as under [11] :-

a) QPSK - Rb/2b) 8 PSK - Rb/3c) 16 PSK - Rb/4d) 64QAM - Rb/6

2.7 C/N ratio required at the input of receiverGenerally, C/N ratio of 18 dB is considered verygood [6]. With technological improvements in thereceiver even 10 dB is considered adequate forgood reception.

2.8 Communication pathCommunication Path (CP) has been included in thevariables, which may be either ‘mobileenvironment’ or ‘free space’. When the height of receiving antenna is sufficiently high (about 120mor so) and if there are no obstacles in thetransmission path, path loss slope may be of freespace rather than mobile environment [6].Secondly, there is a possibility of using the videotransceiver as a repeater, receiving from a fieldsource and transmitting to a GEO satellite, via freespace.

3. Simulation programThe model is simulated in MATLAB. This

algorithm and the formulae/ values developed forvarious parameters can be used by the designer tooptimize transmitter power output, size and heightof receiving antenna etc depending on type andquality of program to be transmitted. By varyingthe inputs one can obtain essential C/N ratio so thatthe communication is achieved in desiredconditions of user.

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3.1 Simulation results

Legend : Bold indicates the changed data ascompared to last serial numberSNo - Serial NumberProg - Type of ProgramQual - Quality RequiredMod - Type of ModulationPt W - Transmitter Powerf GHz - Frequency;

Dtr Km -Distance between Transmitterand Receiver in KmRA - Rain Attenuation :H - Heavy, M - Moderate, N- No Rain

Df m - Depth of Foliage in metres in transmissionpathCP - Communication Path :M - Mobile, F- Free SpaceD m - Diameter of Receiving AntennaHra m -Height of Receiving Antenna

Rb Mbps - Bit RateBn MHz -BandwidthLp dB path loss in dBsPr dB -Power ReceivedC/N - C/N Ratio available

Table 3. Results of simulation

Transmitter Comn Path Receiver Results

SNo Prog Qual Mod PtW

f GHz

DtrKm RA Df

m CP Dm

Hram

RbMbps

BnMHz

LpdB

PrdBm

PndBm

C/ N

1 Sports Good QPSK 5 2 1 N 0 M 0.2 6 6 3 125 -67 -110 43




5 Sports Good QPSK 5 2 1 M 0 M 0.6 6 6 3 154 -87 -110 23

6 Sports Good QPSK 5 2 1 H 0 M 0.6 6 6 3 159 -92 -110 18

7 Sports Good QPSK 5 2 1 M 100 M 0.6 6 6 3 176 -106 -110 4

8 Film Average 64PSK 5 2 1 H 100 M 0.6 6 0.7 0.11 178 -111 -124 13


10 Film Average 64PSK 5 2 15 N 0 M 0.6 10 0.7 0.11 172 -100 -124 24

11 Sports Good QPSK 5 2 15 H 0 M 0.6 60 6 3 182 -95 -110 15

12 Film Average 64PSK 5 2 5 M 500 M 2 60 0.7 0.11 215 -117 -124 7

13 Film Average 64PSK 10 2 5 M 500 M 2 60 0.7 0.11 215 -114 -124 10

14 Film Average 64PSK 5 2 5 M 500 M 2 100 0.7 0.11 215 -113 -124 1115 Film Average 64PSK 5 2 3 M 300 M 0.6 100 0.7 0.11 201 -110 -124 14

16 Film Average 64PSK 5 2 2 M 200 M 0.2 100 0.7 0.11 191 -109 -124 15

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4. Discussion of results (with reference to Table 3)

The results show that it is possible to design a mobile video transceiver for various applications, in differentconditions as under:-

4.1 For News Reporting-

1. S. No 1, 2 and 3, shows that communication up to 1- 3 Km is possible with Transmitter Power of 5 W if Foliage Loss is negligible and there is no rain.

2. S. No 4 shows that communication up to 1 Km is possible with Transmitter Power of 5 W, even if depth of foliage is up to 100 m, but no rain should be there.

3. S. No 5 and 6 show that communication up to 1 Km is possible with Transmitter Power of 5 W, even inheavy rain, if Foliage Loss is negligible.

4. S. No 7and 8 indicate that communication up to 1 Km is possible with Transmitter Power of 5 W, even inheavy rain and depth of foliage is up to 100m, but with a compromised video signal.

4.1.1 Conditions in which communication not Possible

1. S. No 12 indicates that communication is Not OK , even up to 5 Km with 5 W with Receiver Antenna Heightto 60 m, if depth of Foliage is 500m , even in Moderate rain.

4.2 For Defence Applications like enemy area monitoring with un-manned Aerial Vehicle (UAV), etc.

1. S. No 9 and 10 show that communication is Good up to 15 Km with Transmitter Power of 5 W withReceiver Antenna Height to 10 m and with compromised video signal , if no Foliage Loss is there and norain is there.

2. S. No 11 shows that communication is Good up to 15 Km with Transmitter Power of 5 W if Receiver

Antenna Height is 60 m, even in Heavy rain if no Foliage Loss is there.3. S. No 13 shows that communication is possible up to 5 Km with Transmitter Power of 10 W with ReceiverAntenna Height to 60 m, if depth of Foliage is 500m , even in Moderate rain.

4. S. No 14, 15 and 16 show that communication is possible for 2-5 KM, with 5W in moderate rain and varyingfoliage, if antenna height is 100m by optimizing the parameters of the transceiver.

5. Conclusion1. This paper brings out all important aspects in

the design of a Video Transceiver anddeveloped expressions for the factorsaffecting the design.

2. The Simulation program makes the job of designer very simple as he can optimize theparameters and check for its performancebefore manufacturing the transceiver.

3. Video transmission from place of activity toSatellite earth station so far is throughcoaxial cable or a recorded program in CD istransmitted. This paper shows that it ispossible to achieve the communicationbetween a mobile (man-held) videotransmitter from place of activity and a static(or vehicle mounted) Satellite Earth Station

Transceiver for an optimum range withdesired C/N ratio by varying the parametersof the transceivers suitably.

4. By using the simulator developed, it ispossible to design a transceiver for newsreporting and also for defence applications.

6. Acknowledgement The authors express their heart felt

gratitude to Col K.P.C. Rao, Col H.G. Malude andMajor T.K. Balakrishnan of M/s AsterTeleservices, Hyderabad, for their technical supportin the field trials for measuring the signal strength.

References[1] A.M. Dhake, Television and Video

Engineering, Second Edition (TataMcgraw-Hill, 2002, p-583)

[2] R.R. Gulati, Modern Television Practice,Third Edition ( New Age InternationalPublishers,2006, p-647).

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[3] R.R. Gulati, Monochrome and Colour Television, Second Edition , ( New AgeInternational Publishers,2007, p-530).

[4] Timothy Pratt, Charles Bostian andJeremy Allnut, Satellite CommunicationsSecond Edition , (John Wiley & Sons,

Inc,2007 , p-420,110).[5] Major B. Bhikshapathy, V.M.

Pandharipande and P.G. Krishna Mohan,Mobile Path Loss for Indian Suburbanareas, Indian Journal of Science &Technology, Vol 5, No.8 , August 2012

[6] William C.Y.Lee, Mobile Cellular Telecommunications, Analog and DigitalSystems, Second Edition (Tata McGrawHill,2006, p-124,127,118).

[7] G.K. Behera & Lopamudra Das, MobileCommunication (Scitech Publications(India) Ltd, 2008, p-13.33).

[8] M. Richaria, Satellite CommunicationSystems, Design Principles, Second

Edition (John Wiley & Sons 2005, p-76).[9] Timothy Pratt, Charles Bostian and

Jeremy Allnut, Satellite CommunicationsFirst Edition (John Wiley & Sons,Inc,2002, p-342.381).

[10] M/s Advent Technologies, Technicalmanual of AUC 3800 (Advent UpConnect)

[11] Wayne Tomasi, Advanced ElectronicCommunication Systems, VI Edition ,(Pearson Education, 2004, p-86)

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